How to load a csv file in MATLAB by skipping erroneous rows? - matlab

Question

I am using the csvread command to read a large CSV file:
M=csvread('myfile.csv');
But there are few rows in it, apparently, which do not allow MATLAB to load the file because of being text (or otherwise garbage). For example, line number 45372, 117573, etc. So, how do I skip them when loading the file?

Answer 1

When few mean already few you can use try-catch structure in while loop. It is also needed to know number of columns.
Following code expect error message:
Mismatch between file and format string.
Trouble reading number from file (row <row#>, field <field#>) ==> <faulty line content>
The code tries to load whole csv in once. If it fails it analyses error message, identifies the faulty line, loads the file to the line before and appends the result to the data variable. In next run it starts loading one line below the faulty line. This iteration is terminated when the remaining file is succesfully read to the end.
StartRow=<number of ignored rows (header)>;
Ncols=<width>;
data=zeros(0,Ncols);
csvFault=true;
while csvFault
try
Temp=csvread('YourFile.csv',StartRow,0) % Try to read file from StartRow to the end-of-file.
csvFault=false; % Executed only when CSVread is succesful
catch msg
%% Error occured
faultyRow=regexp(msg.message,' ','split'); % Split error message into cells
faultyRow=faultyRow{12}; % 12th cell contain row identifier
faultyRow=str2double(faultyRow(1:end-1)); % Identifier is number followed by 1 letter
%% Read the data from the segment between faulty lines
Temp=csvread('YourFile.csv',StartRow,0,[StartRow,0,faultyRow-1,Ncols-1])
StartRow=faultyRow+1;
end
data=[data;Temp];
end